The present invention relates to a curable resin, and more particularly, it relates to a radically curable resin having a variety of uses, said resin having a pendanted bisphenol diglycidylether type epoxy resin with a polymerizable terminal acryloyl or methacryloyl group. For simplicities sake only, the acryloyl or methacryloyl group will hereinafter be referred to collectively as a (metha)acryloyl group. The present invention also relates to a process for preparing said resin.
Radically curable resins are currently typified by unsaturated polyester resins and vinylester resins, and diallylphthalate resins are also employed as molding material, decorative material and the like.
Each of these resins are appropriately used depending upon their characteristcs and physical properties and are very useful for their respective applications.
However, there are many points for improving the defects present in these resins when they are applied to each of a variety of uses or to any application which demand novel characterics. For example, although vinylester resins exhibit outstanding water-resistance and resistance to chemical agents and are thus employed in large amounts as corrosion resistant FRP and corrosion resistant flake-linings, the production of molding material or of fiber-based prepreg or the provision of useful shaped products from vinylester resins is difficult at present. This is because it is difficult to apply them depending according to pplications for the production of molding material or prepreg due to the fact that vinylesters have a molecular weight of only several hundred to approximately 2000, corresponding to at most oligomers/prepolymers. Thus it is necessary to increase their molecular weight by any means.
From the reasons set forth above, vinylester resins, by way of example, are generally employed in combination with a diisocyanate to react the latter with the hydroxy groups in the former to increase the molecular weight resulting in a thickening of viscosity.
However, this procedure makes it difficult, as a general trend, to consistently obtain the constant viscosity, fluidity, and moldability of the product and thus results in severe fluctuation therein. Moreover, the above procedure may give rise to chemical cross-linking reactions which make it difficult to mold the resultant product. This is an effective reason for inhibiting the widespread use of the resins.
On the other hand, it is only recently that it has become possible to control the thickness of unsaturated polyesters by the formation of metal cross-linkages between the terminal carboxyl groups in said unsaturated polyesters and magnesium oxide resulting from the combined use of unsaturated polyesters and an oxide of divalent metals such as magnesia. However, some fluctuations in moldability still remained and further, the use of alkaline metal oxides may occasionably be disagreeable for some applications such as those demanding high electrical properties.